U.S. patent application number 16/010885 was filed with the patent office on 2018-12-27 for method for manufacturing laser processed product and the laser processed product.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Masaki KOIKE, Junya SHIMOTAMARI, Akira TSUKUI, Hideki YAMAUCHI.
Application Number | 20180369963 16/010885 |
Document ID | / |
Family ID | 64691369 |
Filed Date | 2018-12-27 |
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United States Patent
Application |
20180369963 |
Kind Code |
A1 |
TSUKUI; Akira ; et
al. |
December 27, 2018 |
METHOD FOR MANUFACTURING LASER PROCESSED PRODUCT AND THE LASER
PROCESSED PRODUCT
Abstract
A method for manufacturing a laser processed product including a
laser processed part is performed by using a laser oscillation
section, a beam splitting section and an imaging section. The
manufacturing method includes: forming an irradiation mark
including an irradiation pattern in a reference irradiation surface
by using the laser oscillation section and the beam splitting
section, the irradiation pattern including a plurality of
irradiation spots; obtaining an image of the irradiation mark via
the imaging section; determining a representative position based on
positions of the plurality of irradiation spots in the image;
determining a deviation amount of deviation of the representative
position from a target position; and forming the laser processed
part with a irradiation position corrected based on the deviation
amount.
Inventors: |
TSUKUI; Akira; (Nagoya-shi,
JP) ; KOIKE; Masaki; (Nagoya-shi, JP) ;
SHIMOTAMARI; Junya; (Nishio-shi, JP) ; YAMAUCHI;
Hideki; (Ogaki-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA |
Toyota-shi |
|
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
|
Family ID: |
64691369 |
Appl. No.: |
16/010885 |
Filed: |
June 18, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23K 26/03 20130101;
B23K 26/352 20151001; H01M 2/0434 20130101; B23K 26/60 20151001;
H01M 2/0287 20130101; B23K 26/043 20130101; B23K 26/032 20130101;
H01M 2/0426 20130101; Y02E 60/10 20130101 |
International
Class: |
B23K 26/352 20060101
B23K026/352; B23K 26/03 20060101 B23K026/03; H01M 2/02 20060101
H01M002/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 21, 2017 |
JP |
2017-121637 |
Claims
1. A method for manufacturing a laser processed product including a
laser processed part, the method comprising: forming an irradiation
mark including an irradiation pattern in a reference irradiation
surface by using a laser oscillation section and a beam splitting
section, the laser oscillation section emitting laser light for
irradiation toward a processing object, the beam splitting section
splitting the laser light from the laser oscillation section to
form the irradiation pattern in an irradiation target surface of
the processing object, the irradiation pattern including a
plurality of irradiation spots not arranged in a straight line, the
irradiation pattern including a representative position coinciding
with a direct irradiation position for a case where the laser light
from the laser oscillation section is provided without being split;
obtaining an image of the irradiation mark formed by using the
laser oscillation section and the beam splitting section, via an
imaging section, the imaging section obtaining the image of an area
including a target position in the irradiation target surface;
determining the representative position in the irradiation pattern
based on the positions of the plurality of irradiation spots in the
image; determining a deviation amount of deviation of the
representative position from the target position in the image; and
forming the laser processed part by irradiating the processing
object with the laser light from the laser oscillation section with
an irradiation position in the irradiation target surface corrected
based on the deviation amount, the irradiation position being
irradiated with the laser light from the laser oscillation
section.
2. The method for manufacturing a laser processed product according
to claim 1, wherein the direct irradiation position is included in
the irradiation spots in the irradiation pattern.
3. The method for manufacturing a laser processed product according
to claim 1, wherein for determining the representative position, a
first representative line is determined based on two or more
positions of the plurality of irradiation spots, and a second
representative line that is not parallel to the first
representative line is determined based on other two or more
irradiation spots of the plurality of irradiation spots, and a
position of intersection between the first representative line and
the second representative line is determined as the representative
position.
4. The method for manufacturing a laser processed product according
to claim 1, wherein as the beam splitting section, a diffraction
optical element that diffracts the laser light from the laser
oscillation section is used.
5. The method for manufacturing a laser processed product according
to claim 1, wherein as the reference irradiation surface, a surface
of the processing object is used, the surface including a part to
be processed.
6. The method for manufacturing a laser processed product according
to claim 1, wherein the forming the irradiation mark is performed
for a rough area within a recommended range in which a surface
roughness is determined in advance, in the reference irradiation
surface.
7. The method for manufacturing a laser processed product according
to claim 6, wherein the recommended range is 0.2 .mu.m to 0.25
.mu.m.
8. The method for manufacturing a laser processed product according
to claim 6, the method further comprising forming the rough area
within the reference irradiation surface by roughening a surface of
the processing object, before forming the irradiation mark.
9. The method for manufacturing a laser processed product according
to claim 1, wherein the processing object includes a first outer
covering member and a second outer covering member for a battery,
and the laser processed product is a battery including the first
outer covering member and the second outer covering member welded
to each other via laser processing, the battery incorporating a
power generation element inside.
10. A laser processed product including a laser processed part, the
product comprising: a first laser irradiation mark in the laser
processed part; and a second laser irradiation mark located in a
part of the laser processed part, the part being not a part in
which the first laser irradiation mark is located, the second laser
irradiation mark including an irradiation pattern including a
plurality of irradiation spots not arranged in a straight line.
Description
INCORPORATION BY REFERENCE
[0001] The disclosure of Japanese Patent Application No.
2017-121637 filed on Jun. 21, 2017 including the specification,
drawings and abstract is incorporated herein by reference in its
entirety.
BACKGROUND
1. Technical Field
[0002] The present disclosure relates to a method for manufacturing
a laser processed product including a laser processed part, and a
laser processed product.
2. Description of Related Art
[0003] Conventionally, laser welding for joining two members to
each other via laser light irradiation has been taking place. In
laser welding, it is necessary to provide laser light irradiation
targeted for a position of joining between two members. This is
because low precision of a laser light irradiation position is
highly likely to cause poor welding. Examples of a technique for
correcting a laser light irradiation position for such reason
include Japanese Patent Application Publication No. 2004-276101 (JP
2004-276101 A). In other words, in the laser processing method in
JP 2004-276101 A, an actual measurement value is obtained by
picking up an image of a laser light irradiation position via an
imaging device. Then, a correction value for correcting an offset
distance between the imaging device and a laser head and a
correction value for correcting a distortion of an f.theta. lens
are calculated.
SUMMARY
[0004] However, the above-stated conventional technique has the
following problem. An irradiation mark formed at a laser light
irradiation position is not a point but an area having a certain
degree of breadth. Therefore, it is necessary to identify the
center of the irradiation position. However, the shape of the
irradiation mark is not necessarily a perfect circle and is
sometimes distorted. This is because the laser light energy
distribution itself is not necessarily symmetrical about the
center. Furthermore, the shape of the irradiation mark is also
affected by a property of the irradiation target surface. In a
condition in which a distorted irradiation mark would be formed,
the center of an irradiation position cannot precisely be
identified. Therefore, an increase in precision of correction of
the irradiation position may fail.
[0005] The present disclosure provides a method for manufacturing a
laser processed product, the method enabling performing laser
processing with an irradiation position corrected with high
precision even in a condition in which a distorted irradiation mark
would be formed at a laser light irradiation position. Also, the
present disclosure provides a laser processed product.
[0006] A first aspect of the present disclosure provides a method
for manufacturing a laser processed product including a laser
processed part, in which a laser oscillation section that emits
laser light for irradiation toward a processing object, a beam
splitting section that splits the laser light from the laser
oscillation section to form an irradiation pattern in an
irradiation target surface of the processing object, the
irradiation pattern including a plurality of irradiation spots not
arranged in a straight line, the irradiation pattern including a
representative position coinciding with a direct irradiation
position for a case where the laser light from the laser
oscillation section is provided without being split, and an imaging
section that obtains an image of an area including a laser
processing target position in the irradiation target surface are
used. The method for manufacturing a laser processed product
includes: forming an irradiation mark including the irradiation
pattern in a reference irradiation surface using the laser
oscillation section and the beam splitting section; obtaining an
image of the irradiation mark via the imaging section; determining
a representative position in the irradiation pattern based on
positions of the plurality of irradiation spots, in the image:
determining a deviation amount of deviation of the representative
position from the target position in the image; and forming the
laser processed part by irradiating the processing object with the
laser light from the laser oscillation section with an irradiation
position in the irradiation target surface corrected based on the
determined deviation amount, the position being irradiated with the
laser light from the laser oscillation section.
[0007] In the method for manufacturing a laser processed product
according to the first aspect, a processing object is processed by
irradiating the processing object with laser light from the laser
oscillation section, and a laser processed product is thus
manufactured (processing step). A part irradiated with the laser
light in the processing object becomes a laser processed part.
Here, in the first aspect, prior to the processing step, an amount
of deviation of a laser light irradiation position from a
processing target position is identified. This is intended to
correctly perform processing by performing the processing step with
the deviation corrected. The deviation amount to be identified is a
vector amount.
[0008] For identification of the deviation amount, first, an
irradiation mark is formed by irradiating a reference irradiation
surface with laser light. At this time, use of the beam splitting
section allows the irradiation mark to be formed, to have a
predetermined irradiation pattern including a plurality of
irradiation spots (pattern forming step). Then, an image of the
formed irradiation mark is obtained via the imaging section.
[0009] The irradiation pattern formed by the irradiation mark in
the obtained image includes a plurality of irradiation spots.
Therefore, a representative position in the irradiation pattern can
be determined based on positions of the irradiation spots
(representative position determination step). The determined
representative position is a position coinciding with a direct
irradiation position for the laser light from the laser oscillation
section. However, the position is a position determined through
patterning via the beam splitting section and thus has a small
error relative to a position obtained by forming a welding mark at
the direct irradiation position only and thus is highly precise.
Even if a roundness of each irradiation spot is low, such low
roundness does not matter much. The deviation amount is determined
by comparing the representative position thus determined with a
position determined as a laser processing target position in the
image.
[0010] The processing step is performed with the irradiation
position corrected based on the deviation amount. In the processing
step, the processing object can be irradiated with the laser light
without using the beam splitting section or the processing object
can be irradiated with the laser light using the beam splitting
section. Also, where the processing is welding, the processing
object is formed of a first object and a second object, and a part
of abutment between the first and second objects becomes the laser
processed part (welded part).
[0011] In the first aspect, a spot corresponding to the direct
irradiation position may be included in the irradiation spots in
the irradiation pattern. In this case, the representative position
determined as stated above is a position obtained by correcting the
direct irradiation position based on irradiation spots other than
the direct irradiation spot. Irradiation spots other than the
direct irradiation spot being taken into consideration to determine
the representative position as above enhances the positional
precision.
[0012] In the first aspect, for determining the representative
position, a first representative line may be determined based on
two or more positions of the plurality of irradiation spots, and a
second representative line that is not parallel to the first
representative line may be determined based on other two or more
irradiation spots of the plurality of irradiation spots, and a
position of intersection between the first representative line and
the second representative line may be determined as the
representative position. In this case, as a matter of course, an
irradiation spot group for determining the first representative
line and an irradiation spot group for determining the second
representative line are different irradiation spot groups. However,
the direct irradiation spot may be included in both groups. Here,
the direct irradiation spot does not necessarily need to be used
for determination of the first and second representative lines.
[0013] In the first aspect, as the beam splitting section, a
diffraction optical element that diffracts the laser light from the
laser oscillation section may be used. This is because the
elimination of the need for mechanical scanning of the irradiation
position enables further enhancement in positional accuracy of each
irradiation spot and thus enables higher-precision determination of
the representative position. This is also because a zero-order spot
at a position that is the same as the direct irradiation position
is included in the irradiation pattern.
[0014] In the first aspect, as the reference irradiation surface, a
surface of the processing object, the surface including a part to
be processed may be used. Consequently, determination of the
deviation amount and performance of processing take place on the
same surface of the processing object and thus, higher correction
accuracy can be expected during processing. This is because the
deviation amount is the same between the time of determination of
the deviation amount and the time of performance of processing.
[0015] In the first aspect, forming the irradiation mark may be
performed for a rough area within a recommended range in which a
surface roughness is determined in advance, in the reference
irradiation surface. A smooth area having a small surface roughness
has high laser light reflectivity. Therefore, energy of laser light
necessary for forming an irradiation mark is high. On the other
hand, in the case of an area having an excessively large surface
roughness, a range that is proper for energy of laser light for
forming an irradiation mark is limited to a narrow range on the low
energy side. Forming an irradiation mark in an irradiation mark
having a surface roughness in the recommended range provide the
advantage of a proper energy range for the laser light being
wide.
[0016] In the first aspect, the recommended range may be 0.2 .mu.m
to 0.25 .mu.m.
[0017] Therefore, the rough area may be formed within the reference
irradiation surface by roughening a surface of the processing
object, before the forming the irradiation mark. Consequently, even
if the reference irradiation surface originally includes no proper
rough area, the irradiation mark can properly be formed to
determine the deviation amount.
[0018] In the first aspect, the processing object may include a
first outer covering member and a second outer covering member for
a battery, and the laser processed product may be a battery
including the first outer covering member and the second outer
covering member welded to each other via laser processing, the
battery incorporating a power generation element inside. The first
aspect enables manufacture of a highly reliable battery in which
the first outer covering member and the second outer covering
member are properly welded to each other.
[0019] Also, a laser processed product according to a second aspect
of the present disclosure, which includes a laser processed part,
includes a first laser irradiation mark in the laser processed part
and a second laser irradiation mark located in a part of the laser
processed part, the part being not a part in which the first laser
irradiation mark is located. The second laser irradiation mark has
an irradiation pattern including a plurality of irradiation spots
not arranged in a straight line. The presence of the second laser
irradiation mark enables determining the relevant laser processed
product as one manufactured by the laser processed product
manufacturing method according to the above-described first
aspect.
[0020] The present configuration provides a method for
manufacturing a laser processed product, the method enabling
performing laser processing with a laser light irradiation position
corrected with high precision even in a condition in which a
distorted irradiation mark would be formed at the irradiation
position. Also, the present configuration provides the laser
processed product.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Features, advantages, and technical and industrial
significance of exemplary embodiments of the disclosure will be
described below with reference to the accompanying drawings, in
which like numerals denote like elements, and wherein:
[0022] FIG. 1 is a perspective view illustrating a battery
manufactured via laser welding;
[0023] FIG. 2 is a sectional view illustrating a configuration of a
laser welding apparatus;
[0024] FIG. 3 is a plan view illustrating an example of a shape of
an irradiation mark formed without using a diffraction optical
element;
[0025] FIG. 4 is a plan view illustrating an example of a patterned
irradiation mark formed using a diffraction optical element;
[0026] FIG. 5 is a plan view illustrating an example of an
irradiation mark where irradiation energy is large;
[0027] FIG. 6 is a plan view illustrating irradiation target
surfaces before and after roughening and an irradiation mark
formed;
[0028] FIG. 7 is a graph indicating a reproduction precision of an
irradiation mark forming position for each surface roughness and
each energy density; and
[0029] FIG. 8 is a flowchart illustrating a battery manufacturing
procedure according to a method according to an embodiment.
DETAILED DESCRIPTION OF EMBODIMENTS
[0030] An embodiment of the present disclosure will be described in
detail below with the accompanying drawings. The present embodiment
is one that embodies the present disclosure as a method for
manufacturing a battery 1, which is illustrated in FIG. 1. The
battery 1, which is of a flat rectangular shape, has an outer shape
formed by a case body 2 and a cover member 3. Inside the battery 1,
a power generation element 4 is incorporated. The case body 2 and
the cover member 3 are welded to each other via a welding mark 5
that extends over an entire periphery thereof. The welding mark 5
is one formed by laser welding. Also, positive and negative
electrode terminals 6, 7 are provided so as to extend through the
cover member 3. Furthermore, a rough area 8 is formed in a part of
an outer surface of the cover member 3. The rough area 8 will be
described later.
[0031] A configuration of a laser welding apparatus 9 for welding
the case body 2 and the cover member 3 above to each other will be
described with reference to FIG. 2. The laser welding apparatus 9
illustrated in FIG. 2 includes a laser oscillator 10 and a head
unit 11. The laser oscillator 10 and the head unit 11 are connected
via a fiber cable 12. The head unit 11 is configured to irradiate
an irradiation target surface 26 of a workpiece 25 set below with
laser light emitted from the laser oscillator 10. The laser light
from the head unit 11, the laser light irradiating the workpiece
25, has a capability of locally melting the workpiece 25. In
addition to such capability, the head unit 11 also has a function
that images the irradiation target surface 26.
[0032] In the head unit 11, a collimator lens 13, a diffraction
optical element 17, a dichroic mirror 14, a coaxial camera 15, a
reflective mirror 16, a Z-direction lens drive unit 18, a
reflective mirror 19, a condenser lens 20, an X-Y scanner unit 21,
and a triaxial driver 22 are provided. From among these components,
in the Z-direction lens drive unit 18, a Z-direction lens 23 is
incorporated. Also, in the X-Y scanner unit 21, a galvanometer
mirror 24 is incorporated.
[0033] The collimator lens 13 is a lens that collimates laser light
emitted from the laser oscillator 10. The diffraction optical
element 17 is configured to split laser light from the laser
oscillator 10 to form an irradiation pattern including a plurality
of irradiation spots in the irradiation target surface 26. Details
of the irradiation pattern will be described later. The diffraction
optical element 17 can enter a state in which the diffraction
optical element 17 is disposed on an optical path of laser light
and a state in which the diffraction optical element 17 is
retracted from the optical path. The diffraction optical element 17
illustrated in FIG. 2 is in the state in which the diffraction
optical element 17 is disposed on the optical path of the laser
light.
[0034] The dichroic mirror 14 is an optical element that reflects
light in a particular wavelength range only and transmits light of
wavelengths out of that range. The dichroic mirror 14 in the
present embodiment is configured to reflect laser light emitted
from the laser oscillator 10 and transmits light other than the
laser light. Consequently, the irradiation target surface 26 can be
observed and imaged by the coaxial camera 15 while laser light from
the laser oscillator 10 is provided for irradiation of the
irradiation target surface 26.
[0035] The Z-direction lens drive unit 18 is configured to focus
laser light on the irradiation target surface 26 by upward/downward
movement of the Z-direction lens 23. The X-Y scanner unit 21 is
configured to adjust a position of irradiation with laser light in
the irradiation target surface 26, by driving the galvanometer
mirror 24. Each of the Z-direction lens drive unit 18 and the X-Y
scanner unit 21 is controlled by the triaxial driver 22.
[0036] In the laser welding apparatus 9, a laser pointer 27, a
protection glass plate 28, and an air nozzle 29 are further
provided. The laser pointer 27 is configured to irradiate the
irradiation target surface 26 with a laser beam that is different
from laser light from the head unit 11. The laser beam from the
laser pointer 27 has no capability of melting the workpiece 25 and
is configured to form a bright spot within an image of the
irradiation target surface 26 observed and picked up by the coaxial
camera 15. The laser welding apparatus 9 is adjusted so that a
position of the bright spot becomes a target position of welding
via laser light from the head unit 11. The protection glass plate
28 is configured to prevent laser light from becoming stray light
as a result of the laser light deviating from the workpiece 25. The
air nozzle 29 is configured to blow off foreign substances on the
irradiation target surface 26.
[0037] Welding via the above-described laser welding apparatus 9 is
performed as follows. First, at the time of welding, the
diffraction optical element 17 is brought into the state in which
the diffraction optical element 17 is retracted from the optical
path of laser light. Thus, the irradiation target surface 26 of the
workpiece 25 is irradiated with direct laser light emitted from the
laser oscillator 10 and not subjected to beam splitting by the
diffraction optical element 17. Consequently, the above-described
target position in the irradiation target surface 26 is locally
melted. Therefore, where the workpiece 25 is formed of two members,
a part of abutment between the two members is placed at the target
position, and is irradiated with laser light in such state, whereby
the two members is welded to each other.
[0038] Here, welding may be performed in a state in which the
diffraction optical element 17 runs out on the optical path of
laser light. This is because with the diffraction optical element
17, a plurality of irradiation spots generated include one located
at a position that is the same as a position of direct laser light
(zero-order light). Welding using the diffraction optical element
17 enables a space between the members to be reliably closed using
later-described diffracted light as a secondary heat source while
securing a weld penetration depth using direct laser light
(later-described zero-order light) using a primary heat source.
[0039] In the case of the battery 1, the part of a boundary between
the case body 2 and the cover member 3 may be placed at the target
position, and while the target position being irradiated with laser
light, the battery 1 may be moved so as to cause the target
position to make a circuit of a peripheral edge of the cover member
3. Consequently, the welding mark 5 is formed, and the battery 1 is
thus manufactured. Here, it should be understood that the power
generation element 4 is put in the case body 2 prior to the
welding.
[0040] In the above description, it has been assumed that an
irradiation position, in the irradiation target surface 26,
irradiated with direct laser light from the laser oscillator 10 and
the above-described target position match up precisely with each
other as intended. However, in reality, there may be a certain
degree of deviation between these positions. If there is such
deviation, even though laser light irradiation is performed in such
a manner as described above, proper welding cannot be achieved.
Therefore, in the present embodiment, a direction and an amount of
the deviation are identified using the diffraction optical element
17 and welding is performed with the deviation corrected.
[0041] The deviation amount (vector amount) can simply be
identified by irradiating the irradiation target surface 26 with
direct laser light with the workpiece 25 fixed. In other words, the
direction of the deviation from the target position and the amount
of the deviation may be determined in an image by observing a
generated spot-like irradiation mark in the image via the coaxial
camera 15. As described above, the target position can be
recognized as a bright point in the image, the bright point being
provided by a laser beam from the laser pointer 27. However, as
stated in the above, that is not enough to determine the center
position of the irradiation mark with good precision. This is
because an irradiation mark 30 may be a spot having a distorted
shape that is not a perfect circle as illustrated in FIG. 3.
[0042] Therefore, in the present embodiment, the deviation amount
is identified with higher precision by using the diffraction
optical element 17. The diffraction optical element 17 is an
optical component having a known grid pattern, and is configured to
split laser light from the laser oscillator 10 into a plurality of
laser light beams. Therefore, if an irradiation mark is formed on
the irradiation target surface 26 with the diffraction optical
element 17 inserted on the optical path (FIG. 2), as illustrated in
FIG. 4, a patterned irradiation mark 31 formed of a plurality of
spots is formed.
[0043] The patterned irradiation mark 31 in FIG. 4 is formed of a
zero-order spot 32 at the center and a plurality of diffracted
spots 33 around the zero-order spot 32. The zero-order spot 32 is a
spot formed by zero-order light travelled straight through the
diffraction optical element 17, and is formed at a position that is
the same as a position of an irradiation mark 30 (FIG. 3) where no
diffraction optical element 17 is used. Each diffracted spot 33 is
a spot formed by diffracted light resulting from diffraction via
the diffraction optical element 17. An arrangement pattern of the
respective spots in the irradiation mark 31 is determined by the
grid pattern of the diffraction optical element 17 and a wavelength
of laser light of the laser oscillator 10. In other words, if the
type of the laser oscillator 10 and the grid pattern of the
diffraction optical element 17 are determined, the arrangement
pattern of the irradiation mark 31 is constant. However, as
illustrated in FIG. 5, depending on the irradiation energy, the
respective spots in the irradiation mark 31 may be connected.
[0044] In the patterned irradiation mark 31 in FIG. 4, each of the
spots 32, 33 has the center position thereof. There are several
known methods for determining the center position of each spot 32,
33, and any of such methods may be employed. Examples of the
methods include, e.g., a method in which a center position of each
spot where the spot is regarded as a figure, a method in which the
center position is determined from an approximate image for each
spot and a method in which a circle is put on each spot by Hough
transform and the center position of the circle is used.
[0045] Then, an average position of these center positions can be
obtained. This average position of a representative position for
the entire patterned irradiation mark 31, and is a position that
coincides with the true center position of an irradiation mark 30
(FIG. 3) formed without using the diffraction optical element 17.
Therefore, a direction and an amount of deviation of the
representative position from the target position may be determined
in an image. Even in the case where the irradiation mark 31 has a
continuous shape such as in FIG. 5, the center position of each
spot 32, 33 can be determined by identifying the center position on
a screen.
[0046] As a matter of course, even if the above-described method of
the present embodiment is used, the center position of each spot
32, 33 has a problem in precision because of a reason similar to
that of the case illustrated in FIG. 3. However, employment of the
representative position of the center positions of the plurality of
spots 32, 33 reduces an error in position of each spot 32, 33.
Therefore, in comparison with the case where a deviation amount is
identified from only one spot formed by direct laser light such as
in FIG. 3, in the present embodiment, a deviation amount can be
identified with much higher precision. Even the case in FIG. 5,
which is relatively inferior in precision to the case of FIG. 4,
but still enables identification of a deviation amount with higher
precision compared to the case in FIG. 3.
[0047] In the above, the description has been provided on obtaining
the representative position of the irradiation mark 31 as the
average position of the center positions of the respective spots
32, 33. For an average position of the respective center positions,
an average of coordinate values of the respective center positions
may be obtained for each of an X-coordinate and a Y-coordinate.
Furthermore, not only simply averaging but also weighted averaging
may be used. Weighting in such case may be, for example, weighting
a spot farther from the zero-order spot 32 more. Also, since
distribution of energy among the plurality of divisional laser
light beams is known, a spot with larger energy can be weighted
more. Conversely, a spot with larger energy can be weighted
less.
[0048] Alternatively, instead of obtaining an average position, it
is possible to determine representative lines A, B indicated in
FIG. 4 based on the center positions of the respective spots 32, 33
and set a point of intersection between representative lines A and
B as a representative position. Each of representative lines A, B
is a line determined based on the center positions of a plurality
of spots included in the spots 32, 33. The plurality of spots for
determining representative line A and the plurality of spots for
determining representative line B are different spot groups.
However, the zero-order spot 32 may be included in both groups.
Also, representative line A and representative line B are
non-parallel to each other. More specifically, representative lines
A, B may be determined by means of a least-squares method based on
the center positions of the spots on the respective representative
lines. Also, regardless of whether the average position or the
representative lines are used, the position of the zero-order spot
32 may be excluded from the determination of the representative
position. In particular, where the irradiation mark 31 has a
continuous shape such as in FIG. 5, it is preferable to determine
the representative position with the position of the zero-order
spot 32 excluded.
[0049] After the deviation amount being identified with good
precision in such a manner as described above, welding may be
performed with the deviation amount corrected. For the correction
of the deviation amount, there is a method in which a target
position itself is corrected and a method in which a workpiece 25
is set at a position obtained by back calculation for the deviation
amount from the target position, and either of the methods may be
employed. As a result of irradiation with laser light from the head
unit 11 with the correction for the deviation amount made as
described above, laser light can be applied precisely to the part
of the boundary between the case body 2 and the cover member 3.
Consequently, welding can properly be performed.
[0050] Here, in observing and imaging an irradiation mark 31 formed
in the irradiation target surface 26, such as illustrated in FIG.
4, via the coaxial camera 15, there is the problem of original
smoothness of the irradiation target surface 26. If the smoothness
of the irradiation target surface 26 is excessively high, an
irradiation mark 31 is not easily formed. Since a smooth surface
has high laser light reflectivity, only a small part of input
energy contributes to formation of an irradiation mark 31.
Therefore, laser light for irradiation needs to have quite high
energy.
[0051] Thus, prior to laser light irradiation for formation of an
irradiation mark 31, it is desirable to perform a roughening step
of roughening the irradiation target surface 26. In other words, as
illustrated in FIG. 6, the irradiation target surface 26 (upper
part) is first roughened to form the rough area 8 (middle part).
Within this rough area 8, an irradiation mark 31 is formed (lower
part). As a result of the roughening step being performed in such a
manner as described above, an irradiation mark 31 can stably be
formed with no need for laser light for irradiation to have
particularly high energy. This is because the rough area 8 has low
laser light reflectivity and a majority of input energy effectively
contributes to formation of the irradiation mark 31. Furthermore,
forming the irradiation mark 31 within the rough area 8 also
provides the advantage of a boundary between the inside and the
outside of the irradiation mark 31 being easily and clearly
recognized in an image observed via the coaxial camera 15. This is
because a clear difference in brightness between the inside and the
outside of the irradiation mark 31 appears in the image.
[0052] Therefore, in comparison with the case where an irradiation
mark 31 is performed with no roughening step performed, the center
positions of the respective spots 32, 33 can be determined with
even higher precision. Here, the rough area 8 does not need to be
formed the entire irradiation target surface 26, and it is
sufficient that the rough area 8 is formed in an area including an
entire area in which a patterned irradiation mark 31 is to be
formed. Also, if the irradiation target surface 26 is originally
adequately rough, an irradiation mark 31 may be formed sufficiently
clearly even with no roughening step performed.
[0053] Examples of a specific method of roughening include scanning
a laser light ray on the irradiation target surface 26. A laser
beam of the laser pointer 27 may be used with an output thereof
increased to be higher than that for forming a bright point, or a
laser beam of the laser oscillator 10 may be used with an output
thereof decreased to be lower than that for welding or forming an
irradiation mark 31. Alternatively, roughening may be performed via
mechanical polishing or chemical etching.
[0054] Next, results of tests performed with regard to effects of
roughening will be described. FIG. 7 illustrates reproduction
precisions of forming positions when a multitude of irradiation
marks 31 are formed, for each surface roughness Ra of the rough
area 8 after roughening and each energy density of the laser beam.
Here, the energy density of the laser beam is not that for a laser
beam used in the roughening step, but the energy density of the
laser beam for forming an irradiation mark 31. In FIG. 7, the
abscissa axis represents surface roughness Ra [m], and the ordinate
axis represents energy density [J/mm.sup.2] of the laser beam.
[0055] The figures plotted in FIG. 7 each indicate a degree of
reproducibility of a forming position when an irradiation mark 31
is formed with the relevant surface roughness and the relevant
energy density. More specifically, each of the degrees is ranked as
".largecircle.", which indicates 25 .mu.m or less, ".DELTA.", which
indicates 25 to 45 .mu.m, or "x", which indicates 45 .mu.m or more,
according to standard deviation of coordinate values of positions
of the multitude of irradiation marks 31 formed.
[0056] Referring to FIG. 7, while in the right-side part in the
graph in which the surface roughness is large, tests were conducted
under a condition that the energy density is not so high, in the
left-side part in the graph in which the surface roughness is
small, tests were conducted under respective conditions ranging
from a condition that the energy density is low to a condition that
the energy density is high. This is because, as described above, an
irradiation mark 31 can be formed on a rough surface even with a
laser beam of low energy, but a clear irradiation mark 31 cannot
easily be formed on a smooth surface unless a laser beam of high
energy is used.
[0057] In FIG. 7, furthermore, within a surface roughness Ra range
of 0.1 to 0.3 .mu.m, only results of ".largecircle." or ".DELTA."
are indicated. In particular, within a surface roughness Ra range
of 0.2 to 0.25 .mu.m, only results of ".largecircle." are
indicated. Therefore, these ranges are ranges recommended for the
surface roughness Ra of the rough area 8.
[0058] For example, under the condition that the surface roughness
Ra is 0.25 .mu.m and the energy density is approximately 250
J/mm.sup.2, an irradiation mark 31 such as illustrated in FIG. 4 in
which respective spots can clearly be recognized individually was
formed, and variation of the center positions of the respective
spots was 25 .mu.m or less. Also, under the condition that the
surface roughness Ra is approximately 0.13 .mu.m and the energy
density is approximately 250 J/mm.sup.2, an irradiation mark 31
such as illustrated in FIG. 5 was formed. In the irradiation mark
31, spots were connected, but the center position of each spot
could be at least determined, and variation of the center positions
of the respective spots was within a range of 25 to 45 .mu.m. Under
the condition that the surface roughness Ra is approximately 0.13
.mu.m, also, variation of the center positions of respective spots
was 25 .mu.m or less when the energy density was increased to
around approximately 500 J/mm.sup.2.
[0059] On the other hand, under a condition that the surface
roughness Ra is high and exceeds approximately 0.3 .mu.m, even with
a low energy density of approximately 130 J/mm.sup.2, a sufficient
irradiation mark 31 was not formed because of excessive melting.
Even with visual identification of the center position of each
spot, variation of the center positions exceeded 45 .mu.m. However,
even under such roughness condition, variation of the center
positions of the respective spots can be made to 45 .mu.m or less
if the energy density is further decreased.
[0060] Also, under the condition that the surface roughness Ra is
0.05 .mu.m and thus low and the energy density is approximately 250
J/mm.sup.2 or less, a sufficient irradiation mark 31 was not formed
because of insufficient weld penetration. With visual
identification of the center position of each spot, variation of
the center positions exceeded 45 .mu.m. However, even under such
roughness condition, variation of the center positions of the
respective spots fell to 45 .mu.m or less when the energy density
was increased to approximately around 500 J/mm.sup.2 or more.
Therefore, even though the surface roughness Ra of the rough area 8
is out of the aforementioned recommended ranges, such rough area 8
is not totally unusable.
[0061] According to the above, manufacture of the battery 1 in FIG.
1 by the laser welding apparatus 9 according to the present
embodiment, that is, welding between the case body 2 and the cover
member 3, is performed according to the procedure in FIG. 8. In
other words, a workpiece 25 (a case body 2 and a cover member 3) is
set at an irradiation target position (S1), and first, a rough area
8 is formed through the roughening step (S2). In the example
illustrated in FIG. 1, the rough area 8 is formed at a position in
an upper surface of the cover member 3, the position not
overlapping a welding mark 5. In reality, the rough area 8 is
formed prior to the welding mark 5.
[0062] Then, a patterned irradiation mark 31 is formed within the
rough area 8 (S3). Although illustrated not so precisely in FIG. 1,
in reality, an irradiation mark 31 is also formed within the rough
area 8 in the battery 1 illustrated in FIG. 1. Then, a deviation
amount is determined (S4). As described above, the deviation amount
is determined by observation and imaging of an irradiation mark 31
via the coaxial camera 15, determination of a representative
position of the irradiation mark 31 and identification of a
deviation amount (vector amount) via comparison between the
representative position and a target position (bright point
provided by the laser pointer 27). Then, welding is performed with
the deviation corrected (S5). Consequently, a welding mark 5 is
formed.
[0063] In the above description of the procedure in FIG. 8, the
formation of the rough area 8 in step S2 is performed for the upper
surface of the cover member 3. This means that the patterned
irradiation mark 31 is formed at a part that is level with a
welding target part. Therefore, there is almost no difference in
amount of deviation of an irradiation position from a target
position between the time of formation of the irradiation mark 31
and the time of performance of welding. Therefore, the accuracy for
correction of deviation is higher. Here, depending on the original
surface roughness of the upper surface of the cover member 3, the
step in S2 may be omitted.
[0064] Also, the steps in S2 to S4 in the procedure in FIG. 8 may
be performed for all of individual batteries 1 to be subjected to
welding or may be performed for a representative one only. In the
latter case, based on a deviation amount obtained for the
representative one, the other ones are subjected to correction and
welding in a manner that is similar to those of the representative
one. Here, e.g., immediately after a start of the laser welding
apparatus 9 from a stop state or after a large change in air
temperature or other environmental factor, it is desirable to
perform the steps in S2 to S4 without fail. This is because the
deviation amount possibly varies.
[0065] As described in detail above, with the present embodiment,
when two members are to be welded to each other by the laser
welding apparatus 9, a deviation of a welding position, that is, a
laser light irradiation position for welding, from a target
position is corrected. An amount of the deviation is identified by
forming a patterned irradiation mark 31 such as illustrated in FIG.
4, rather than a single spot. Consequently, in comparison with the
case where a deviation amount is identified based on a single spot,
a deviation amount can be identified with higher precision.
Therefore, an intended position can correctly be irradiated with
laser light and thus proper welding can be performed.
[0066] Also, desirably, prior to forming the irradiation mark 31, a
rough area 8 is formed in an irradiation target surface 26. Thus,
the patterned irradiation mark 31 is formed within the rough area
8, a laser light reflectivity of which is not so high. Therefore,
the patterned irradiation mark 31 can properly be formed without
the need to increase energy of laser light for forming the
irradiation mark 31 to be so high.
[0067] Note that the present embodiment is a mere example and does
not limit the present disclosure in any way. Therefore, it should
be understood that various improvements and alterations of the
present disclosure are possible without departing from the spirit
of the disclosure.
[0068] For example, the pattern of the irradiation mark 31 formed
on the irradiation target surface 26 prior to the welding step is
not limited to those illustrated in, e.g., FIG. 4. At a minimum,
the pattern may be a pattern meeting the following two conditions.
In other words, the two conditions are that: all of spots are not
arranged on a straight line; and a representative position in the
entire pattern can be calculated by any sort of arithmetic
processing based on positions of the respective spots. In the case
of a pattern in which all spots are arranged in a straight line, a
representative position cannot properly be determined as a
two-dimensional coordinate position, and thus, such pattern is not
proper. Besides the orthogonal four-direction pattern illustrated
in FIG. 4, a six-direction or eight-direction pattern, a T-shaped
pattern or a three-direction pattern is conceivable.
[0069] Also, in the above embodiment, a beam splitting section that
splits laser light from the laser oscillator 10 into a plurality of
laser light beams, the diffraction optical element 17 is used.
However, what can be used as the beam splitting section is not
limited to the diffraction optical element 17. As the beam
splitting section other than the diffraction optical element 17,
for example, mechanically scanning a laser light irradiation
position itself is conceivable. The mechanical scanning may be
performed by operating the galvanometer mirror 24 of the X-Y
scanner unit 21 or moving a workpiece 25 itself. Both may be used.
However, it is undeniable that this method is inferior to the case
where the diffraction optical element 17 is used, in terms of
reproducibility of spot positions because of an error accompanying
a mechanical scan.
[0070] Still another example of the beam splitting section can be a
birefringent element. A birefringent element needs no mechanical
movement other than advancement and retraction relative to the
optical path of laser light and thus has a property similar to the
diffraction optical element 17 in causing no aforementioned
mechanical error. However, a pattern formed via a birefringent
element does not necessarily naturally includes a spot at a
position that is the same as that of direct laser light, and in
such respect, a birefringent element is inferior to the diffraction
optical element 17. Here, an optical element including both a
diffraction optical element and a birefringent element may be
used.
[0071] Furthermore, the embodiment described above is an embodiment
of the present disclosure for welding using the laser welding
apparatus 9. However, processing performed for an object by laser
light from the laser oscillator 10 is not limited to welding.
Examples of laser processing other than welding can include cutting
and surface modification (if the object includes a surface coating
layer, including removal of such layer). In those cases, a cut part
or a modified part corresponds to a laser processed part. Also, in
particular, in the case of surface modification, at the time of
processing being performed, whether or not to use the diffraction
optical element 17 (beam splitting section) can be selected.
* * * * *